Re: Topband: Short receiving verticals question
Thanks Tom and others for detailed comments on this issue. I understand the focus on bandwidth, presumably to keep the phasing constant across 100 kHz or less of 160 meters, and see how that would be important with fixed phasing. But in my bs/ef, the two forward elements are fed in phase (equal-length feed lines to a T) and so are the two rearward ones. The two feedlines from these Ts then run to the shack where a DX Engineering NCC-1 (W8JI design) is used to adjust the phasing between the two sets of elements. I'm thinking the variable phasing should compensate for any changes in phasing across the band due to narrow bandwidth of the elements, or any changes from variation due to proximity to trees or in tree foliage change through the seasons. At worst I would need to re-adjust the phasing control as I QSY up and down the band. But maybe there's another issue I'm missing. My first RX bs/ef has only been functioning a few weeks, including the CW 160m contest, and is still a work in progress. For now the 23-foot elements are fed directly with the feedline center conductor (no series coil and resistor yet) so are resonant around 80 meters. They do have the top hat wires though they are tied off rather haphazardly to convenient trees. And the equal-length feedlines from the elements to the Ts are simply laid on the ground, with no choking toroids at the feedpoint nor a ground rod for the shield out 15 feet from the feedpoint as I use on Beverage feedlines. About 100 feet of the two hardline runs going to the NCC-1 are buried closest to the house. There is a ground rod at the T junction. Elements have twenty 25-foot radials and are tied to a 2-3 ft. ground rod and the coax shield at each feedpoint. I'm using 75 ohm Pentabond CATV cable for the four equql feedlines (184 feet each) and 3/4 inch CATV 75 ohm hardline from the Ts to the shack. Because the elements are not yet matched/tuned for 160, their output is lower than the Beverages. Even at this development stage, I have found this array to be almost always better for hearing Europe than any of the three phased Beverage pairs I have (535 ft and 750 ft stagger phased and 950 ft with 200 ft broadside spacing). It is really cool to flip the switch to reverse the phasing and see the difference in f/b, and also to tune through the phasing range and find other peaks available from the continuous 0-360 degree adjustment, and to optimize the f/b to null out signals and noise off the rear. I also found this array had some useful f/b on 80 meters despite the very wide broadside spacing (but the endfire spacing is 1/4 wave on 80). The f/b on 160 meters on the short verticals is significantly better than from any of the Beverages in nulling out a persistent, intermittent local noise from the southwest that I've been unable to track down. I like W3LPL's suggestion to use the 7-foot posts to keep the wires above deer level. And also a tip from WW4B to use lightweight fishing line to tie off the ends, making this the weak link in the system, so any falling tree branches will snap this line rather than the element itself or the wire. Replacing the fishing line will be a lot easier than repairing an element or wire in terms of ongoing, long-term maintenance. I'll adopt both of these ideas here. 73/Jon AA1K On 1/30/2014 5:24 AM, Tom W8JI wrote: But what about an element loaded with a coil at the center or at the top? Would there be advantages to that approach that would come close to the short verticals with top-hat wires, or any serious disadvantages? Jon, The reason I use the hats and do everything I do in the elements is bandwidth. Even at my quiet rural location on the quietest hour of the quietest day, almost any element of reasonable height will have more than enough signal level. This is why I base load and use a large hat. While the large hat tends to keep current more uniform throughout the element independent of coil location, and while more uniform current increases radiation resistance, that effect is meaningless to me. The entire goal for me is bandwidth, or a stable SWR vs. frequency. Bandwidth is also why I load the element with a series resistance for matching, instead of a network. I want to swamp out or dilute the effects of resonance, minimizing element phase shift vs. frequency change at the element terminals and preventing drastic changes in element feedpoint impedance from mutual coupling between elements. The hat is actually the bulk of the loading, and sets the current distribution. The coil just cancels reactance. Since it is a series network with the inductor forming a series tank with the termination reactance, the lower the reactance used (compared to termination resistance) the larger bandwidth becomes. You want the loading coil to be terminated in the lowest capacitive reactance possible, and that is at the antenna base. Because voltage and current are
Re: Topband: Short receiving verticals question
Hi Jon, I've also found that my four phased short verticals consistently outperform my Beverages, especially when arrival angles are low. Sometimes I can copy signals on the phased averticals that I can't even hear on the Beverages. Its easy to tuine the short verticals to 160 meters. I use inexpensive 10 and 18 microhenry fixed chokes (less than a dollar each from Mouser) and a few 1/2 watt resistors in series. I installed two RF ports on each tuning box. A 50 ohm BNC port is used only to tune the vertical to R=50, Z=0 at 1835 kHz. A 25 ohm resistor (measured on a digital ohm meter) connects the 50 ohm test port to the 75 ohm F connector. Use BNC and F connectors with four mounting holes, they won't loosen up from multiple cable connects/disconnects. Avoid the common cheap stamped metal F connectors, any side pressure from the cables with snap them. You should replace your T-connectors with zero-degree phase hybrid combiners (sometimes called magic Ts or 3 dB splitters). I'll send you a copy of W1MK's letter in May 2011 QEX by separate e-mail. 73 Frank W3LPL - Original Message - From: Jon Zaimes AA1K j...@verizon.net To: Tom W8JI w...@w8ji.com, topband topband@contesting.com Sent: Saturday, February 1, 2014 5:07:02 PM Subject: Re: Topband: Short receiving verticals question Thanks Tom and others for detailed comments on this issue. I understand the focus on bandwidth, presumably to keep the phasing constant across 100 kHz or less of 160 meters, and see how that would be important with fixed phasing. But in my bs/ef, the two forward elements are fed in phase (equal-length feed lines to a T) and so are the two rearward ones. The two feedlines from these Ts then run to the shack where a DX Engineering NCC-1 (W8JI design) is used to adjust the phasing between the two sets of elements. I'm thinking the variable phasing should compensate for any changes in phasing across the band due to narrow bandwidth of the elements, or any changes from variation due to proximity to trees or in tree foliage change through the seasons. At worst I would need to re-adjust the phasing control as I QSY up and down the band. But maybe there's another issue I'm missing. My first RX bs/ef has only been functioning a few weeks, including the CW 160m contest, and is still a work in progress. For now the 23-foot elements are fed directly with the feedline center conductor (no series coil and resistor yet) so are resonant around 80 meters. They do have the top hat wires though they are tied off rather haphazardly to convenient trees. And the equal-length feedlines from the elements to the Ts are simply laid on the ground, with no choking toroids at the feedpoint nor a ground rod for the shield out 15 feet from the feedpoint as I use on Beverage feedlines. About 100 feet of the two hardline runs going to the NCC-1 are buried closest to the house. There is a ground rod at the T junction. Elements have twenty 25-foot radials and are tied to a 2-3 ft. ground rod and the coax shield at each feedpoint. I'm using 75 ohm Pentabond CATV cable for the four equql feedlines (184 feet each) and 3/4 inch CATV 75 ohm hardline from the Ts to the shack. Because the elements are not yet matched/tuned for 160, their output is lower than the Beverages. Even at this development stage, I have found this array to be almost always better for hearing Europe than any of the three phased Beverage pairs I have (535 ft and 750 ft stagger phased and 950 ft with 200 ft broadside spacing). It is really cool to flip the switch to reverse the phasing and see the difference in f/b, and also to tune through the phasing range and find other peaks available from the continuous 0-360 degree adjustment, and to optimize the f/b to null out signals and noise off the rear. I also found this array had some useful f/b on 80 meters despite the very wide broadside spacing (but the endfire spacing is 1/4 wave on 80). The f/b on 160 meters on the short verticals is significantly better than from any of the Beverages in nulling out a persistent, intermittent local noise from the southwest that I've been unable to track down. I like W3LPL's suggestion to use the 7-foot posts to keep the wires above deer level. And also a tip from WW4B to use lightweight fishing line to tie off the ends, making this the weak link in the system, so any falling tree branches will snap this line rather than the element itself or the wire. Replacing the fishing line will be a lot easier than repairing an element or wire in terms of ongoing, long-term maintenance. I'll adopt both of these ideas here. 73/Jon AA1K On 1/30/2014 5:24 AM, Tom W8JI wrote: But what about an element loaded with a coil at the center or at the top? Would there be advantages to that approach that would come close to the short verticals with top-hat wires, or any serious disadvantages? Jon, The reason I use the hats
Re: Topband: Short receiving verticals question
Most of those birds and other winged predators have been seen or heard here and keep the rodents managable. I take care of some squirrels and chipmunks with .22 shorts in a rifle and a competition grade air rifle. The white tail rats are everywhere since there are several apple and pear trees plus a 150 x 150 field of various berries to keep them happy year around. I clear cut that a few years ago and let the ground clutter under the trees get some sun...WOW! We also have coyote, fox and fisher cats, plus a few bears to help with population control. There are still miles of undeveloped land abutting or close to me. Carl KM1H - Original Message - From: Joe Subich, W4TV li...@subich.com To: topband@contesting.com Sent: Thursday, January 30, 2014 2:42 PM Subject: Re: Topband: Short receiving verticals question A possible answer might be here: http://www.legupenterprises.com/ Doesn't faze the deer around here. They come right up to the house and the fenced kennels and munch on whatever they like. That stuff may do something with the small animals but the Eagle, Great Horned Owl, Red Tail Hawk and other birds of prey generally keep the rodents and small mammals in check. 73, ... Joe, W4TV On 1/30/2014 1:42 PM, Gary Smith wrote: The biggest problem with the top hat is deer catching the wire/string and bending the element or some rodent eating the string. A possible answer might be here: http://www.legupenterprises.com/ They sell predator urine which discourages animals from going near the smell. My YL uses it to keep the squirrels out of her flowers and it works extremely well. I just had my antenna wires clipped by a rabbit over last weekend (saw the tracks in the snow) and I put some coyote urine in a vial the company sells and have that at my radial plate. I'm sure it'll work as well for keeping them away here as it does in her garden. If it would have tried chewing the 160 Inv-L while I was working the contest I might have had a nice supper. Gary KA1J --- This email is free from viruses and malware because avast! Antivirus protection is active. http://www.avast.com _ Topband Reflector Archives - http://www.contesting.com/_topband _ Topband Reflector Archives - http://www.contesting.com/_topband _ Topband Reflector Archives - http://www.contesting.com/_topband
Re: Topband: Short receiving verticals question
ON4UN describes a method of over swamping the base of the topless verticals used in his four-square receive array to acheive wider bandwidth. On 80M, he switches in additional series resistance to arrive at a total feedpoint resistance of 300 ohm, then steps down to 75 ohm using a split winding 4:1 (2T:1T ratio) transformer (also helps mitigate common-mode). This effectively increases operating bandwidth. See section 1.28 The Mini Receiving Four Square at ON4UN in Chapter 7 / Receiving Antennas, Fifth Edition. I am doing some experiments with a 630M BSEF (8-circle) and have a test element currently using the same concept (though it is top loaded). 1.2:1 bandwidth was originally a mere 5 kHz. With the additional swamping resitance and step-down, it is now around 20 kHz. 73 Eric NO3M _ Topband Reflector Archives - http://www.contesting.com/_topband
Re: Topband: Short receiving verticals question
ON4UN describes a method of over swamping the base of the topless verticals used in his four-square receive array. On 80M, he switches in additional series resitance to arrive at a total feedpoint resistance of 300 ohm, then steps down to 75 ohm using a split winding 4:1 (2T:1T ratio) transformer (also serves to mitigate common-mode). This effectively increases operating bandwidth. See section 1.28 The Mini Receiving Four Square at ON4UN in Chapter 7 / Receiving Antennas, Fifth Edition. I am doing some experiments with a 630M element currently using the same concept (though it is top loaded). 1.2:1 bandwidth was originally a mere 5 kHz. With the additional swamping resitance and step-down, it is now at least around 20 kHz. 73 Eric NO3M _ Topband Reflector Archives - http://www.contesting.com/_topband
Re: Topband: Short receiving verticals question
But what about an element loaded with a coil at the center or at the top? Would there be advantages to that approach that would come close to the short verticals with top-hat wires, or any serious disadvantages? Jon, The reason I use the hats and do everything I do in the elements is bandwidth. Even at my quiet rural location on the quietest hour of the quietest day, almost any element of reasonable height will have more than enough signal level. This is why I base load and use a large hat. While the large hat tends to keep current more uniform throughout the element independent of coil location, and while more uniform current increases radiation resistance, that effect is meaningless to me. The entire goal for me is bandwidth, or a stable SWR vs. frequency. Bandwidth is also why I load the element with a series resistance for matching, instead of a network. I want to swamp out or dilute the effects of resonance, minimizing element phase shift vs. frequency change at the element terminals and preventing drastic changes in element feedpoint impedance from mutual coupling between elements. The hat is actually the bulk of the loading, and sets the current distribution. The coil just cancels reactance. Since it is a series network with the inductor forming a series tank with the termination reactance, the lower the reactance used (compared to termination resistance) the larger bandwidth becomes. You want the loading coil to be terminated in the lowest capacitive reactance possible, and that is at the antenna base. Because voltage and current are out-of-phase above the coil, even with high current, the impedance increases. This means the tradeoff in a bottom inductance is increased voltage above the inductor. The antenna is more loss critical above the coil for anything coupled via the electric field, including a lossy dielectric. This is a compromise of two things: 1.) Bandwidth 2.) Sensitivity to dielectrics around the element Getting rid of the hat while the element is close to a tree does nothing but bad things to both, but no one can say how much. The last resort for me would be no hats. Perhaps you can use T elements with loading wires away from foliage that might change tuning or losses? 73 Tom _ Topband Reflector Archives - http://www.contesting.com/_topband
Re: Topband: Short receiving verticals question
I have used this same setup for my 4-square 160m receive array for years. Since I have to take down and put up this array every spring/fall, I have to re-tune each element for the 160m band. I have found that the base loading does not have to be exact for the system to 'work'. Last year I decided to make inductor substitution box for each element to easily tune each element close to 1.830 MHz. The biggest problem with the top hat is deer catching the wire/string and bending the element or some rodent eating the string. It's amazing how forgiving aluminum tubing is as I can straighten it many times without breaking. At the base I use a 2 ft ground rod and 4 short radials. I found the use of the ground rod makes a large change in the tuning of the element. Doug -Original Message- Jon, The reason I use the hats and do everything I do in the elements is bandwidth. Even at my quiet rural location on the quietest hour of the quietest day, almost any element of reasonable height will have more than enough signal level. This is why I base load and use a large hat. While the large hat tends to keep current more uniform throughout the element independent of coil location, and while more uniform current increases radiation resistance, that effect is meaningless to me. The entire goal for me is bandwidth, or a stable SWR vs. frequency. Bandwidth is also why I load the element with a series resistance for matching, instead of a network. I want to swamp out or dilute the effects of resonance, minimizing element phase shift vs. frequency change at the element terminals and preventing drastic changes in element feedpoint impedance from mutual coupling between elements. The hat is actually the bulk of the loading, and sets the current distribution. The coil just cancels reactance. Since it is a series network with the inductor forming a series tank with the termination reactance, the lower the reactance used (compared to termination resistance) the larger bandwidth becomes. You want the loading coil to be terminated in the lowest capacitive reactance possible, and that is at the antenna base. Because voltage and current are out-of-phase above the coil, even with high current, the impedance increases. This means the tradeoff in a bottom inductance is increased voltage above the inductor. The antenna is more loss critical above the coil for anything coupled via the electric field, including a lossy dielectric. This is a compromise of two things: 1.) Bandwidth 2.) Sensitivity to dielectrics around the element Getting rid of the hat while the element is close to a tree does nothing but bad things to both, but no one can say how much. The last resort for me would be no hats. Perhaps you can use T elements with loading wires away from foliage that might change tuning or losses? 73 Tom _ Topband Reflector Archives - http://www.contesting.com/_topband --- This email is free from viruses and malware because avast! Antivirus protection is active. http://www.avast.com _ Topband Reflector Archives - http://www.contesting.com/_topband
Re: Topband: Short receiving verticals question
Ok Frank I will forward this to the Topband reflector. Bernie McClenny, W3UR Editor of The Daily DX and The Weekly DX www.dailydx.com 410-489-6518 Sent from my iPhone On Jan 30, 2014, at 10:56, donov...@starpower.net wrote: Hi Burny, When you have a chance, please forward this email to the Topband reflector. For some reason its spam filter is blocking emails from me! tks Frank From: donov...@starpower.net To: topband@contesting.com Sent: Thursday, January 30, 2014 3:52:24 PM Subject: Re: Topband: Short receiving verticals question Hi Doug, A few notes about the short verticals in my 160M passive receive array. I use them in my W8JI broadside-endfire passive array described in detail on Tom's home page and on W5ZN's home page. Its important to understand that the loss in the radial system of a 160M passive receive array is of no importance, but variations in the base impedance of the verticals during wet and dry weather could affect the pattern of the array. You don't need many radials, but you do need enough. I use eight 65 foot radials under each vertical. Several of my verticals are in wetlands that flood during wet weather and the variation in ground conditions under the verticals is unusually severe. I initially used four radials and found there was nearly ten ohms change in the resistive component of the feed point impedance between flooded conditions and extreme dry ground conditions. Four additional radials solved that problem. My radials are simply laid on the surface of the ground. While the deer traffic rearranges the location of the radials, that doesn't seem the affect the performance of the array. I use stranded copper wire, solid wire would easily entrap the legs of the deer. Dozens of deer inhabit the field where my verticals are located. I eliminated deer collisions with the umbrella wires by attaching the ends of bottom ends of the wires to the top of seven foot fence posts (through a porcelain insulator and short length of light rope). I've never had a deer collision since. While some users of short verticals install foundations, I've found it completely unnecessary with guyed (e.g. top loaded) verticals. I simply use a two foot length of one inch diameter rebar. The vertical is attached to a 1.25 inch o.d. aluminum tube that simply slips over the rebar. Rebar is very inexpensive and easy to install an remove and especially convenient for temporary installations like mine 73 Frank W3LPL From: Doug Renwick ve...@sasktel.net To: topband topband@contesting.com Sent: Thursday, January 30, 2014 3:04:02 PM Subject: Re: Topband: Short receiving verticals question I have used this same setup for my 4-square 160m receive array for years. Since I have to take down and put up this array every spring/fall, I have to re-tune each element for the 160m band. I have found that the base loading does not have to be exact for the system to 'work'. Last year I decided to make inductor substitution box for each element to easily tune each element close to 1.830 MHz. The biggest problem with the top hat is deer catching the wire/string and bending the element or some rodent eating the string. It's amazing how forgiving aluminum tubing is as I can straighten it many times without breaking. At the base I use a 2 ft ground rod and 4 short radials. I found the use of the ground rod makes a large change in the tuning of the element. Doug -Original Message- Jon, The reason I use the hats and do everything I do in the elements is bandwidth. Even at my quiet rural location on the quietest hour of the quietest day, almost any element of reasonable height will have more than enough signal level. This is why I base load and use a large hat. While the large hat tends to keep current more uniform throughout the element independent of coil location, and while more uniform current increases radiation resistance, that effect is meaningless to me. The entire goal for me is bandwidth, or a stable SWR vs. frequency. Bandwidth is also why I load the element with a series resistance for matching, instead of a network. I want to swamp out or dilute the effects of resonance, minimizing element phase shift vs. frequency change at the element terminals and preventing drastic changes in element feedpoint impedance from mutual coupling between elements. The hat is actually the bulk of the loading, and sets the current distribution. The coil just cancels reactance. Since it is a series network with the inductor forming a series tank with the termination reactance, the lower the reactance used (compared to termination resistance) the larger bandwidth becomes. You want the loading coil to be terminated in the lowest capacitive reactance possible, and that is at the antenna base. Because voltage and current are out-of-phase above the coil, even with high current, the impedance increases. This means the tradeoff in a bottom inductance is increased
Re: Topband: Short receiving verticals question
Hi Doug, A few notes about the short verticals in my 160M passive receive array. I use them in my W8JI broadside-endfire passive array described in detail on Tom's home page and on W5ZN's home page. Its important to understand that the loss in the radial system of a 160M passive receive array is of no importance, but variations in the base impedance of the verticals during wet and dry weather could affect the pattern of the array. You don't need many radials, but you do need enough. I use eight 65 foot radials under each vertical. Several of my verticals are in wetlands that flood during wet weather and the variation in ground conditions under the verticals is unusually severe. I initially used four radials and found there was nearly ten ohms change in the resistive component of the feed point impedance between flooded conditions and extreme dry ground conditions. Four additional radials solved that problem. My radials are simply laid on the surface of the ground. While the deer traffic rearranges the location of the radials, that doesn't seem the affect the performance of the array. I use stranded copper wire, solid wire would easily entrap the legs of the deer. Dozens of deer inhabit the field where my verticals are located. I eliminated deer collisions with the umbrella wires by attaching the ends of bottom ends of the wires to the top of seven foot fence posts (through a porcelain insulator and short length of light rope). I've never had a deer collision since. While some users of short verticals install foundations, I've found it completely unnecessary with guyed (e.g. top loaded) verticals. I simply use a two foot length of one inch diameter rebar. The vertical is attached to a 1.25 inch o.d. aluminum tube that simply slips over the rebar. Rebar is very inexpensive and easy to install an remove and especially convenient for temporary installations like mine 73 Frank W3LPL - Original Message - From: Doug Renwick ve...@sasktel.net To: topband topband@contesting.com Sent: Thursday, January 30, 2014 3:04:02 PM Subject: Re: Topband: Short receiving verticals question I have used this same setup for my 4-square 160m receive array for years. Since I have to take down and put up this array every spring/fall, I have to re-tune each element for the 160m band. I have found that the base loading does not have to be exact for the system to 'work'. Last year I decided to make inductor substitution box for each element to easily tune each element close to 1.830 MHz. The biggest problem with the top hat is deer catching the wire/string and bending the element or some rodent eating the string. It's amazing how forgiving aluminum tubing is as I can straighten it many times without breaking. At the base I use a 2 ft ground rod and 4 short radials. I found the use of the ground rod makes a large change in the tuning of the element. Doug -Original Message- Jon, The reason I use the hats and do everything I do in the elements is bandwidth. Even at my quiet rural location on the quietest hour of the quietest day, almost any element of reasonable height will have more than enough signal level. This is why I base load and use a large hat. While the large hat tends to keep current more uniform throughout the element independent of coil location, and while more uniform current increases radiation resistance, that effect is meaningless to me. The entire goal for me is bandwidth, or a stable SWR vs. frequency. Bandwidth is also why I load the element with a series resistance for matching, instead of a network. I want to swamp out or dilute the effects of resonance, minimizing element phase shift vs. frequency change at the element terminals and preventing drastic changes in element feedpoint impedance from mutual coupling between elements. The hat is actually the bulk of the loading, and sets the current distribution. The coil just cancels reactance. Since it is a series network with the inductor forming a series tank with the termination reactance, the lower the reactance used (compared to termination resistance) the larger bandwidth becomes. You want the loading coil to be terminated in the lowest capacitive reactance possible, and that is at the antenna base. Because voltage and current are out-of-phase above the coil, even with high current, the impedance increases. This means the tradeoff in a bottom inductance is increased voltage above the inductor. The antenna is more loss critical above the coil for anything coupled via the electric field, including a lossy dielectric. This is a compromise of two things: 1.) Bandwidth 2.) Sensitivity to dielectrics around the element Getting rid of the hat while the element is close to a tree does nothing but bad things to both, but no one can say how much. The last resort for me would be no hats. Perhaps you can use T elements with loading wires away from
Re: Topband: Short receiving verticals question
At the speeds that deer run across an open field, I doubt that repellant will help. Seven foot fence posts work perfectly, and they will last a lifetime! 73 Frank W3LPL - Original Message - From: Gary Smith g...@ka1j.com To: Topband@contesting.com Sent: Thursday, January 30, 2014 6:42:57 PM Subject: Re: Topband: Short receiving verticals question The biggest problem with the top hat is deer catching the wire/string and bending the element or some rodent eating the string. A possible answer might be here: http://www.legupenterprises.com/ They sell predator urine which discourages animals from going near the smell. My YL uses it to keep the squirrels out of her flowers and it works extremely well. I just had my antenna wires clipped by a rabbit over last weekend (saw the tracks in the snow) and I put some coyote urine in a vial the company sells and have that at my radial plate. I'm sure it'll work as well for keeping them away here as it does in her garden. If it would have tried chewing the 160 Inv-L while I was working the contest I might have had a nice supper. Gary KA1J --- This email is free from viruses and malware because avast! Antivirus protection is active. http://www.avast.com _ Topband Reflector Archives - http://www.contesting.com/_topband _ Topband Reflector Archives - http://www.contesting.com/_topband
Re: Topband: Short receiving verticals question
A possible answer might be here: http://www.legupenterprises.com/ Doesn't faze the deer around here. They come right up to the house and the fenced kennels and munch on whatever they like. That stuff may do something with the small animals but the Eagle, Great Horned Owl, Red Tail Hawk and other birds of prey generally keep the rodents and small mammals in check. 73, ... Joe, W4TV On 1/30/2014 1:42 PM, Gary Smith wrote: The biggest problem with the top hat is deer catching the wire/string and bending the element or some rodent eating the string. A possible answer might be here: http://www.legupenterprises.com/ They sell predator urine which discourages animals from going near the smell. My YL uses it to keep the squirrels out of her flowers and it works extremely well. I just had my antenna wires clipped by a rabbit over last weekend (saw the tracks in the snow) and I put some coyote urine in a vial the company sells and have that at my radial plate. I'm sure it'll work as well for keeping them away here as it does in her garden. If it would have tried chewing the 160 Inv-L while I was working the contest I might have had a nice supper. Gary KA1J --- This email is free from viruses and malware because avast! Antivirus protection is active. http://www.avast.com _ Topband Reflector Archives - http://www.contesting.com/_topband _ Topband Reflector Archives - http://www.contesting.com/_topband
Topband: Short receiving verticals question
Recent success here with 23-foot-high W8JI-style short receiving verticals in a 4-element broadside/endfire array using variable phasing has led me to make plans for other sets to cover additional directions. To maximize distance from existing and potential noise sources, and to allow for tighter endfire spacing, I chose to make these independent arrays rather than the classic 8-circle array. Since these will all be in a wooded area, I am considering using different elements without top loading wires, to avoid constant maintenance as falling tree limbs would break the wires. I've read of the 36-foot-high base-loaded elements ON4UN described in his book, and understand these would have a slightly narrower bandwidth than an element with top-hat wires. But what about an element loaded with a coil at the center or at the top? Would there be advantages to that approach that would come close to the short verticals with top-hat wires, or any serious disadvantages? 73/Jon AA1K _ Topband Reflector Archives - http://www.contesting.com/_topband
Re: Topband: Short receiving verticals question
On 1/29/2014 6:25 PM, Jon Zaimes AA1K wrote: I've read of the 36-foot-high base-loaded elements ON4UN described in his book, and understand these would have a slightly narrower bandwidth than an element with top-hat wires. But what about an element loaded with a coil at the center or at the top? Would there be advantages to that approach that would come close to the short verticals with top-hat wires, or any serious disadvantages? 73/Jon AA1K I once built a 4x2 fixed array using 30 foot verticals, the height chosen because I had a bunch of 30 foot long irrigation pipes. I not only did not use top loading, but I didn't resonate them with a coil either. Thus the signal was low, but usable. This array worked perfectly, with directivity as per theory. So I think you will be fine w/o top loading wires, especially if you use a resonator coil. The reason not to use a resonator coil is if you want to use the array on more than one band. My array had quarter wave end fire spacing on 80, and eighth wave spacing on 160. It even worked on the broadcast band with a little gain, but a lot of F/B ratio. Rick N6RK _ Topband Reflector Archives - http://www.contesting.com/_topband
